Definition
Known limitations and inaccuracies in the radar imagery produced by the Next Generation Weather Radar (NEXRAD) system. These include ground clutter, range attenuation (weakening of the radar beam over distance), the cone of silence directly above each radar site, false echoes from terrain or non-weather objects, and the time delay between when the radar scans the weather and when the image reaches the cockpit. NEXRAD imagery shown on a Multi-Function Display (MFD) can be several minutes old, even though the timestamp may suggest otherwise.
Plain English
NEXRAD radar pictures of weather are not perfect. They can miss things, show false returns, and are always a few minutes behind real time. Pilots need to know what NEXRAD gets wrong so they don't trust it for close-in decisions about thunderstorms.
Context Anchor
Seen when using an electronic flight display or multi-function display to view NEXRAD weather during preflight planning or in flight.
Derivation
NEXRAD stands for Next Generation Radar — the network of ground-based Doppler radars operated by the National Weather Service. 'Abnormalities' here means the known ways the system's output can be wrong or misleading, not random glitches.
Why Pilots Care
These can create false impressions of storms or clear air, leading to poor route decisions or unnecessary weather avoidance.
Analogy
It is like looking at traffic on a map that is a few minutes old and may have a smudge on it. The map is useful, but you should not treat every detail as perfect or current.
Grounding Statement
What you see on the screen happened a few minutes ago — the storm has already moved and may have grown.
Intuition Check
Do not assume an abnormality is just a minor display flaw. In this context, an abnormality can mean the weather picture is misleading enough to affect a flight decision.
Example Sentence 1
The instructor reminded the student that NEXRAD abnormalities, especially the latency in the displayed image, made the cockpit weather product unsuitable for picking a path between thunderstorm cells.
Example Sentence 2
Range folding appeared as NEXRAD abnormalities on the MFD, prompting the pilot to verify conditions with onboard weather radar.